The Custom List app considers User Stories to be parents. When opting to display the Parent column, see that it reads: Parent (User Story). Essentially only User Stories are being considered as parents.
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Features are also displayed in the Parent column and there is an additional Feature column where the features are also displayed.
So, in order to have no parents displayed in the Parent column at all , the query you will need to set is;
((Parent = “null”) and (Feature = “null”))
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